Protein deficiency is a major health problem throughout the developing world. Low protein intake contributes to mental retardation, stunting, susceptibility to disease, wasting diseases and/or death in hundreds of millions of children each year (Forrester et al., PloS one 7: e35907 (2012); Gomes et al., J. Neuroscience Res. 87: 3568-3575 (2009)).
Plants provide over 60% of human dietary protein (Young et al., Am. J. Clin. Nutr. 59: 1203S-1212S (1994)). Increasing the protein content of staple crops could help alleviate protein deficiency, particularly when the use of animals requires about 100 times more water and 11 times more energy to produce an equivalent amount of protein (Pimentel et al., Am. J. Clin. Nutr. 78: 6605-6635 (2003)) and increasing the protein content of animals is often accompanied by a decrease in protein quality or yield (Bellaloui et al., Agricultural Sciences 1: 110-118 (2010); Wenefrida et al., J. Agricultural Food Chem. 61: 11702-11710 (2013)).
The Arabidopsis thaliana QQS (At3g30720, Qua-Quine Starch) orphan gene modulates protein content in Arabidopsis. Arabidopsis thaliana starch synthase 3 (Atss3) mutants, which are morphologically similar to wild-type (WT) control lines but differ in starch levels (Zhang et al., Plant Physiol. 138: 663-674 (2005)), have more than five-fold the amount of QQS transcripts found in WT (Li et al., Plant J. 58: 485-498 (2009)). Over-expression of QQS in Arabidopsis increases total protein content and decreases total starch content in leaves, while down-regulation of QQS has the converse effect (Li et al., Plant Biotech. J. 13: 177-187 (2015); Li et al. (2009), supra). Expression of QQS as a transgene increases protein content in other plants, such as soybean (var. Williams 82; Li et al. (2014), supra; Li et al. (2009), supra).
QQS expression has been observed to be tightly linked with a variety of developmental, environmental, and genetic perturbations (see, e.g., Arendsee et al., Trends in Plant Sci doi:10.1016/j.tplants.2014.07.003 (2014); Li et al. (2009), supra; and Li et al. (2015), supra). Its role, however, in such perturbations has not been elucidated. For example, PEN3 (Penetration Resistance 3 (At1g59870, PEN3, ABC binding cassette transporter gene) confers non-host resistance to fungal and oomycete pathogens. QQS has been reported to be the only gene that is up-regulated in pen3 knock-out (KO) mutants; however, QQS is up-regulated in infected and non-infected mutants (Stein et al., Plant Cell 18(3): 731-746 (2006)). As another example, two syntaxins, namely SYP121 (At3g11820, PEN1) and SYP122 (At3g52400) confer resistance to powdery mildews. Knock-outs of these genes result in increased sensitivity to these pathogens; QQS has been reported to be the only gene that is up-regulated in both (Zhang et al. (2008)). In contrast, while PEN3 and EXL1 are up-regulated following exposure to some pathogens, QQS is down-regulated in response to infection by some pathogens, such as Pseudomonas syringae (Kwon et al., Planta 236(3): 887-900 (2012); and Thilmony et al., Plant J. 46(1): 34-53 (2006)). When Arabidopsis plants were inoculated with Phytopthera infestans, QQS reportedly was first down-regulated at 6 hrs post-inoculation and then up-regulated at 12 and 24 hrs post-inoculation (Scheel et al., Experiment ID “E-GEOD-5616” in ArrayExpress).
Thus, in view of the above, it is an object of the present disclosure to identify a gene with which QQS interacts. In Arabidopsis QQS interacts with nuclear factor Y, subunit C4 (NF-YC4, At5g63470). It is another object to provide materials and methods for manipulating a gene so identified. In an embodiment, the manipulation of such a gene results in increased protein content and/or decreased carbohydrate content. It is yet another object to provide materials and a method for increasing a plant's resistance to a pathogen or a pest. These and other objects, as well as inventive features, will be apparent from the detailed description provided herein.